I think that just getting 4.0 out the door is very important right now. This will help to "gel" the community and provide a reference foundation for moving forward.
4..0+ should focus heavily on two fronts:
Games development
Let's get the missing/partially complete API's completed - this means the new graphic driver system as well as the 3D support.
I don't know what else is missing/incomplete in 4.0 - sound and/or input APIs? I think they are all pretty much taken care of.
Any compatibility libraries that can help ports from Win/Mac/Linux/PS2/XBox/whatever couldn't hurt either.
Open-source development/ports.
Build a release that encourages ports of open-source products such as OpenOffice, PostgreSQL, Apache, etc.
Provide as many UNIX-compatibility libraries as possible to make the porting process slick!
Many of these products are approaching the feature-completeness and stability of the equivalent commercial offerings.
Having good solid ports of the most popular development environments (i.e. gcc) would be a great first step.
About LINUX
I personally think Linux is just too complicated for the desktop. Too many ways to boot (LILO or GRUB), too many ways too install (name that distribution), turf wars over the "better" frond-end (i.e. KDE or ??), etc... Good luck supporting the unique combo someone is running.
Amiga is in a nice sweet-spot - not bloated like Windows (and dare I say Linux). It just needs more beefing up. I see no reason why with enough "kernel" and filesystem work it can't excel at things like serving up web pages and databases alongside MS and the Linux camp.
That's my 2c. Flame away.